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The Effects of Sleep Restriction on Adolescents' Pedestrian Safety

Background and Purpose

Every year, over 8,000 adolescents ages 14 and 15 require medical attention due to pedestrian injury (National Center for Injury Prevention and Control, 2010). Many factors contribute to safe pedestrian behavior. Among them are reaction time, impulsivity, risktaking, attention, and decision-making (Thomson, 1997). These same characteristics that influence pedestrian safety are also influenced by sleep restriction. Adolescents require a minimum of 8.5 hours of uninterrupted sleep each night.

Despite the fact that adolescents need more sleep than other children, they often do not obtain adequate sleep. One reason is due to shifts in their circadian rhythm, the “clock” that sets humans’ sleep/wake rhythm. During adolescence, the circadian rhythm is delayed, causing them to fall asleep later (Giannotti, Cortesi, Sebastiani, & Ottaviano, 2002). Also at this age, parents begin to decrease their supervision while adolescents desire more independence, while the adolescents have greater academic demands, are involved in more extracurricular activities, and respond more strongly to peer pressure (Carskadon, Wolfson, Acebo, Tzischinsky, & Seifer, 1998). However, they must wake up before their natural sleep pattern has completed due to early school times, causing adolescents to obtain inadequate amounts of sleep. This may put adolescents at greater risk for pedestrian injury.

The overarching aim of this study is to investigate the effects of sleep restriction on adolescents’ pedestrian safety. Using a withinsubjects design, adolescents ages 14 and 15 years old will engage in a virtual pedestrian environment both after an adequate night’s sleep (8.5 hours sleep the previous night) and when they are sleep restricted (4 hours sleep the previous night). There are four specific hypotheses: 1) adolescents will have lower average attention to traffic while crossing a virtual street when sleep restricted than when adequately rested, 2) adolescents will leave less amount of time between safely crossing the street and the next vehicle arriving when sleep restricted than when adequately rested, 3) adolescents will have greater temporal delays between beginning to cross the street after a car passes when sleep restricted than when adequately rested, and 4) adolescents will have a greater number of hits or close calls with a virtual vehicle when sleep restricted than when adequately rested.

Design and Methods

This study will investigate whether sleep restriction reduces adolescents’ pedestrian safety. Sixty adolescents will engage in a virtual reality pedestrian environment in two conditions: a sleep deprived condition and an adequate sleep condition. Sleep quality and quantity will be measured by actigraphy. Actigraphy is a noninvasive, objective measure for detecting patterns of movement during the night. Thus, it yields objective measurements of sleep patterns over time. The participant will wear the actigraph watch from the time of the screening to the end of the study. Actigraph data will be downloaded at each visit to confirm that participants slept the required amount of time the previous night.

In the virtual environment, adolescents will stand on a wooden “curb,” immersed inside three screens simulating a street crossing, and vehicles will pass on the screen. After deciding it is safe to cross, the adolescent will step off the curb, and an avatar will cross the street. Adolescents will receive reinforcement for safely crossing the street or encouragement to try again after failing. Four indicators of safe pedestrian street crossing will assess the safety of crossings: 1) average start delay (time in seconds after a car passes and before participants initiate crossing); 2) average safety time (latency in seconds between participants safely crossing the street and the next vehicle arriving in crosswalk); 3) hits or close calls (when participants would be struck by a vehicle in the real environment, or when the gap between participants and the oncoming vehicle is less than one second); and 4) attention to traffic (number of times participants look left and right before beginning to cross street, divided by the average time in seconds waiting to cross).

Potential Clinical/Research Implications

The study will have broad implications in two areas. First, it will educate policy decisions, such as school start times. Due to research showing that inadequate sleep can lead to decreased academic performance, school start times have emerged as a topic of great debate (Hansen, Janssen, Schiff, Zee, & Dubocovich, 2005). If adolescents are at greater risk for pedestrian injury after obtaining insufficient amounts of sleep, then there might be additional support for policy delaying school start times in order to allow adolescents more time to sleep.

Second, research demonstrating the increased pedestrian risk of sleep restricted adolescents might promote parental enforcement of earlier bedtimes on nights before adolescents will be engaging in pedestrian environments (or, alternatively, encourage parents to drive their adolescents to school on mornings when they were unable to sleep an adequate amount). Each of these outcomes could ultimately result in fewer pedestrian injuries in adolescents.

Overall, this study will raise awareness about the significance of adequate sleep in adolescents and will promote healthier sleep habits.